The present invention relates to a printing machine which is provided with a cleaning device for cleaning the especially sheet-like or continuous-feed printing substrates supplied to the printing machine, whereby the cleaning device comprises a compressed air conduit extending perpendicularly to the direction of transport of the printing substrates and having compressed air outlets oriented toward the printing substrate. The compressed air conduit is essentially arranged centrally within a slotted nozzle connected to a vacuum source such that on opposite sides of the compressed air conduit slot portions are formed.
The particles to be removed from the printing substrate (paper surface) are, in general, non-stick agents that prevent adhesion between stacked or adjacent paper layers.
A cleaning device disclosed in German patent 20 06 716 for removing by vacuum dust from the endless printing substrates supplied to the printing machine is based on the principle that a combined compressed air and suction air system optimizes the cleaning effect. Based on the assumption that the drawings of this German patent application are representative for the size of the cleaning device, the suction box having individual suctions slots and the compressed air conduit (blower box) arranged within has a total width which corresponds to approximately 14 to 19 times the opening width of the compressed air outlets while the compressed air conduit (blower box) has a total width which is approximately 10 to 14 times the width of the compressed air outlets. The printing substrate to be cleaned is thus subjected, due to the great width of the suction box, to an increased electrostatic charge. This carries the risk that, due to the suction slots spaced at a relatively great distance to the compressed air outlets, the dust particles initially removed from the printing support by the compressed air will again settle on the printing substrate. This tendency can be counteracted only to a minimal extent by providing multiple rows of compressed air outlets.